Canon MP490 series On-Screen Manual page 299

Important
Photo Optimizer PRO does not function when:
Background is set in the Stamp/Background dialog box on the Page Setup tab.
Define Stamp... is selected in the Stamp/Background dialog box on the Page Setup tab, and the
bitmapped stamp is configured.
Note
Depending on images, the Photo Optimizer PRO may have no discernible effect.
Page top